The 60 GHz band is an unlicensed band which features a large amount of bandwidth and a large worldwide overlap. The large bandwidth means that a very high volume of information can be transmitted wirelessly. As a result, multiple applications, each requiring transmission of large amounts of data, can be developed to allow wireless communication around the 60 GHz band. Examples for such applications include, but are not limited to, wireless high definition TV (HDTV), wireless docking stations, wireless Gigabit Ethernet, and many others.
In order to facilitate such applications there is a need to develop integrated circuits (ICs), such as amplifiers, mixers, radio frequency (RF) analog circuits, and active antennas that operate in the 60 GHz frequency range. An RF system typically comprises active and passive modules. The active modules (e.g., a phased array antenna) require control and power signals for their operation, which are not required by passive modules (e.g., filters). The various modules are fabricated and packaged as radio frequency integrated circuits (RFICs) that can be assembled on a printed circuit board (PCB). The size of the RFIC package may range from several to a few hundred square millimeters.
In the consumer electronics market, the design of electronic devices, and thus RF modules integrated therein, should meet the constraints of minimum cost, size, power consumption, and weight. The design of the RF modules should also take into consideration the current assembled configuration of electronic devices, and particularly handheld devices, such as laptop and tablet computers, in order to enable efficient transmission and reception of millimeter wave signals. Furthermore, the design of the RF module should account for minimal power loss of receive and transmit RF signals and for maximum radio coverage.
A schematic diagram of a RF module 100 designed for transmission and reception of millimeter wave signals is shown in FIG. 1. The RF module 100 includes an array of active antennas 110-1 through 110-N connected to a RF circuitry or IC 120. Each of the active antennas 110-1 through 110-N may operate as transmit (TX) and/or receive (RX) antennas. An active antenna can be controlled to receive/transmit radio signals in a certain direction, to perform beam forming, and for switching from receive to transmit modes. For example, an active antenna may be a phased array antenna in which each radiating element can be controlled individually to enable the usage of beam-forming techniques.
In the transmit mode, the RF circuitry 120 typically performs up-conversion, using a mixer (not shown in FIG. 1), to convert intermediate frequency (IF) signals to radio frequency (RF) signals. Then, the RF circuitry 120 transmits the RF signals through the TX antenna according to the control signal. In the receive mode, the RF circuitry 120 receives RF signals through the active RX antenna and performs down-conversion, using a mixer, to IF signals using the local oscillator (LO) signals, and sends the IF signals to a baseband module (not shown in FIG. 1).
In both receive and transmit modes, the operation of the RF circuitry 120 is controlled by the baseband module using a control signal. The control signal is utilized for functions, such as gain control, RX/TX switching, power level control, beam steering operations, and so on. In certain configurations, the baseband module also generates the LO and power signals and transfers such signals to the RF circuitry 120. The power signals are DC voltage signals that power the various components of the RF circuitry 120. Normally, the IF signals are also transferred between the baseband module and the RF circuitry 120.
In common design techniques, the array of active antennas 110-1 to 110-N are implemented on the substrate upon which the IC of the RF circuitry 120 is also mounted. An IC is fabricated on a multi-layer substrate and metal vias that connect between the various layers. The multi-layer substrate may be a combination of metal and dielectric layers and can be made of materials, such as a laminate (e.g., FR4 glass epoxy, Bismaleimide-Triazine), ceramic (e.g., low temperature co-fired ceramic LTCC), polymer (e.g., polyimide), PTFE (Polytetrafluoroethylene) based compositions (e.g., PTFE/Cermaic, PTFE/Woven glass fiber), and Woven glass reinforced materials (e.g., woven glass reinforced resin), wafer level packaging, and other packaging, technologies and materials. The cost of the multi-layer substrate is a function of the area of the layer; the greater the area of the layer, the greater the cost of the substrate.
Antenna elements of the array of active antennas 110-1 to 110-N are typically implemented by having metal patterns in a multilayer substrate. Each antenna element can utilize several substrate layers. In conventional implementations for millimeter wave communications, antenna elements are designed to occupy a single side of the multi-layer substrate side. This is performed in order to allow the antenna radiation to properly propagate.
For example, a RF module 200 depicted in FIG. 2 includes a multi-layer substrate 210 and a plurality of antenna elements 220 implemented on an upper layer of the substrate 210. The antenna elements 220 are connected to a RF circuitry 230 using traces 201. The RF circuitry 230 performs the function discussed in greater detail above. The RF module 200 may also contain discrete electronic components 240 such as an antenna interface in an implementation of chip-board transition structure, which typically includes the IC (chip) package and transmission lines from the IC to the substrate. Additionally, circuits designed for impedance matching and electrostatic discharge (ESD) protection may also be part of the antenna interface.
The conventional RF designs require implementing the number of active antennas on one side of the substrate, thus providing a constraint that limits the number of antennas of the RF module. An attempt to increase the number of active antennas would require increasing the area of substrate. Also, such an attempt would require increasing the length of the wires (traces) from the RF circuitry to the antenna elements. Furthermore, simply increasing the number of antenna elements on one side of the multi-layer substrate would limit the performance of the RF module, and may not meet the constraints of an efficient design. Such constraints necessitate that the physical dimensions, the power consumption, heat transfer, and cost should be as minimal possible.
A critical constraint in designing a RF module with multiple active antennas is the ground planes. The ground plane provides a potential reference to RF signals transmit/received by the antennas. Thus, an attempt to design an RF module with a plurality of antennas will not be completed without providing a proper reference ground to each active antenna. A RF module in which the ground planes that do not provide a proper reference to the antennas would causes signal losses.
It would be therefore advantageous to provide an efficient IC layout design for an antenna array connectivity that overcomes the disadvantages of conventional layout design.